JPH01162712A - Method and device for smelting reduction - Google Patents

Abstract

PURPOSE:To produce a molten iron from iron ore with high thermal efficiency by preheating the powdery iron ore with the exhaust gas from a top blowing converter type refining furnace, then preheating and prereducing the ore further with a prereduction furnace and charging the iron into the refining furnace at the time of reducing the iron ore with carbonaceous material by using the above-mentioned refining furnace, thereby executing iron making and refining. CONSTITUTION:The lumped iron ore, carbonaceous material and slag forming material are charged by a chute 14 into the converter type refining furnace 10 provided with a top blowing lance 21 and side face and bottom tuyeres 25, 26. Gaseous O2 is blown from the nozzle 22 of the lance 21 to burn the carbonaceous material and to smelt and reduce the raw materials, by which the molten iron 11 and molten slag 12 are formed. The exhaust gas is subjected to secondary combustion of CO by the gaseous O2 from the nozzle 23 of the lance 21 and is introduced as the exhaust gas having 300-1100 deg.C and 0.4-0.8 degree of oxidation to a preheating prereduction furnace 30 through a dust separator 16. After the powder iron ore is heated by absorbing the sensible heat of the exhaust gas in a heat exchanger 40 utilizing the exhaust gas, the ore is further heated and prereduced to <=30% in the preheating prereduction furnace 30; thereafter, the iron ore is supplied through chutes 31 and 14 into the refining furnace 10, by which the iron ore is reduced to the molten iron.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention provides a smelting reduction method and apparatus for reducing ore in a molten state in a converter-type smelting furnace using carbonaceous materials as fuel and reducing material. Regarding.

[Conventional technology] The smelting reduction method is an alternative to the blast furnace iron making method, and it eliminates the disadvantages of the blast furnace iron making method, such as the high construction cost and the need for a large site. , and in addition to iron,
It has been developed in recent years as a device that can directly reduce chromium, manganese, and nickel ores.

In this reduction method, ore is pre-reduced in a preheating pre-reducing furnace using exhaust gas from the smelting furnace and charged into the smelting furnace together with carbon material and slag material, and oxygen gas or stirring gas is It is blown into the smelting furnace.

Then, the carbonaceous material is dissolved in the previously charged hot metal, and the carbon in the carbonaceous material and the molten metal is oxidized by the oxygen gas. The ore is melted by the oxidation heat at this time, and the ore is reduced by the carbonaceous material and C in the molten metal.

The CO gas generated from the hot metal is subjected to secondary combustion by the excessively blown oxygen gas and becomes CO2 gas. This CO2
The sensible heat of the gas is transferred to the slag overlying the hot metal and the iron particles suspended in the slag, and then to the hot metal.

In this way, the ore is reduced to produce molten metal, but in order to reduce the iron ore reduction process in the smelting furnace, the preliminary reduction rate of the iron ore before being charged into the smelting furnace is set at 60 to 75%.
Therefore, the exhaust gas from the smelting furnace uses a large amount of highly reducing gas with a low oxidation degree. (For example, special public Sho 6l-4
3406) [Problems to be Solved by the Invention] However, in order to increase the preliminary reduction rate to 30% or more, it is necessary to lower the degree of oxidation (hereinafter simply referred to as OD) of the exhaust gas from the smelting furnace. In this case, the amount of exhaust gas will inevitably increase, and the energy generated by the smelting furnace will be 1.0 to 1.5 Gcal/, which is considered to be appropriate.
T (molten, pig iron) will be greatly exceeded, and the generated energy will be excessive in terms of the energy balance within the factory. This naturally leads to an increase in manufacturing costs.

In addition, in order to obtain a high pre-reduction rate, the exhaust gas with a low OD is required as described above, and the residence time of the iron ore in the pre-reduction furnace is lengthened, so that the pre-reduced iron ore is It is difficult to balance the charging cycle of the hot metal into the smelting furnace and the tapping cycle of the produced hot metal. This inevitably greatly limits the degree of freedom in operating the smelting furnace.

Furthermore, in the conventional method, powdery ore generated in the preheating pre-reducing furnace or preheating device is discharged outside the furnace, which is a major factor in reducing the yield of ore. Furthermore, when this is recovered and blown into the tuyeres or oxygen lances of the smelting furnace, there is a risk that coarse particles may be mixed in and cause problems such as clogging of the tuyeres or oxygen nozzles.

The present invention was made to solve these problems, and it is possible to reduce the energy generated from the smelting furnace, improve the energy efficiency of the entire process, and improve the yield of ore and improve operability. The present invention attempts to provide a reduction method and apparatus.

[Means and methods for solving the problems] The smelting reduction method according to the first invention involves preheating and prereducing ore in a fluidized bed type preheating prereduction furnace, and loading the ore into a smelting furnace together with carbonaceous materials and slag making materials. The ore is melted and reduced by blowing oxygen from a top-blowing oxygen lance with an oxygen nozzle for decarburization and secondary combustion, and blowing stirring gas through the grooves provided on the side wall and bottom of the smelting furnace. The method includes controlling the temperature of the gas introduced from the smelting furnace to the preheating pre-reduction furnace from 300 to 1100.
°C, the degree of oxidation of the gas produced in the smelting furnace [(H2O+C
O2) / (H2 + H2O + CO + CO Part or all of the separated fine particles are returned to the preheating pre-reduction furnace, and if there is any remaining, it is mixed with plain or powdered coal material and blown into the smelting furnace through the tuyere or oxygen lance. It is characterized by - The smelting reduction device of the second invention preheats and pre-reduces ore in a fluidized bed type preheating pre-reduction furnace and charges it into a smelting furnace together with carbon material and slag material for decarburization and secondary combustion. A device for melting and reducing ore by blowing oxygen from a top-blown oxygen lance with an oxygen nozzle and blowing stirring gas from tuyere provided on the side wall and bottom of the smelting furnace, and is used for powder injection. the oxygen lance having a nozzle;
A first separation device that separates powder from the exhaust gas of the smelting furnace, a second separation device that separates the powder from the exhaust gas of the preheating pre-reduction furnace, and exhaust gas and raw material supply for the second separation device. It is characterized by comprising a preheating device that preheats the ore introduced from the device, and a third separation device that separates fine ore from the exhaust gas of the preheating device 40.

[Example] Embodiments of the invention will be described with reference to the accompanying drawings.

FIG. 1 is an explanatory diagram of a melt reduction apparatus used in the melt reduction method of the present invention. Inside the smelting furnace 10, an iron bath 11 and a slag layer 12 are formed, and an oxygen lance 21 for blowing oxygen is formed.
is inserted vertically into the furnace. The lance is provided with nozzles 22 and 23 for ejecting oxygen for decarburization and oxygen for secondary combustion, respectively, and furthermore, a nozzle 24 is provided at the center of the tip of the lance for injecting auxiliary materials such as carbonaceous material or lime. ing.

Further, in the upper part of the smelting furnace 10, iron ore as a raw material, carbonaceous material and slag forming material as auxiliary materials are supplied using a well-known conventional raw material supply device (not particularly shown) or a preheating pre-reduction device which will be explained later. A chute 14 for raw materials charged into the smelting furnace by gravity falling from the furnace and an exhaust gas conduit 15 through which exhaust gas from the smelting furnace is discharged are provided. a first separation device 16 for removing dust contained in the exhaust gas discharged from the conduit 15; a fluidized bed preheating pre-reduction furnace 30 into which the exhaust gas and ore are introduced and preheating and pre-reducing them; A second separator 35 receives the exhaust gas from the preheating pre-reduction furnace 30 and removes iron ore particles contained therein, and a second separator 35 receives the exhaust gas from the preheating pre-reduction furnace 30 and removes iron ore particles from the exhaust gas from the second separator 35 and the raw material supply device. A preheating device 40 is introduced to preheat the ore.
and a third separator 45 for removing iron ore fine particles from the exhaust gas from the preheating device 40.

Fine grains or powder of iron ore separated from the first to third separators are mixed with a carrier gas such as Ar and N2, and are pressurized and provided on the side wall and bottom of the smelting furnace, respectively. A pressurizing device 27.
28 is provided.

The operation of the present invention using the melting reduction apparatus configured as described above will be explained. Iron ore, which is a raw material, enters the preheating device 40 from the raw material supply device and is preheated here and then charged into the preheating and pre-reducing furnace. The raw material is charged into the smelting furnace 10 via the raw material chute 14. The auxiliary raw materials in the form of lumps or coarse particles supplied from the raw material supply device are charged into the smelting furnace 10 by falling naturally from the raw material chute 14, and the auxiliary raw materials in the form of fine particles or powder are fed to the nozzle 24 of the oxygen lance or through the tuyere. From 25.26, it is blown into the smelting furnace together with carrier gas.

Further, the exhaust gas generated in the smelting furnace 10 passes through the gas conduit 15, and after dust is removed by the first separation device 16, it is introduced into the fluidized bed type preheating pre-reduction furnace 30, where it acts as a fluidized gas. Iron ore charged into the preheating pre-reducing furnace 30 is preheated and pre-reduced. The exhaust gas from the preheating pre-reduction furnace enters the second separator 35 where fine or powdered ore is separated and introduced into the preheater 40. The exhaust gas from the preheating device 40 is separated into fine grains or powdery ore in a third separator 45, and then discharged through a normal exhaust gas treatment device, or is discharged through a carrier gas from the tuyeres 25 and 26 where the raw powder is injected. used as. Furthermore, this exhaust gas can be mixed with the exhaust gas from the smelting furnace and used for cooling.

Part of the fine or powdered iron ore separated by the second separator is returned to the preheating pre-reduction furnace, and the remainder is mixed with plain or powdered carbon material and sent to the pressurizing device 27, 28. Here, it is mixed with carrier gas and pressurized to the tuyere 25.2.
6, and is charged through the tuyere on the side wall or bottom of the smelting furnace. The fine iron ore separated and recovered by the second separator is mixed with lumpy or coarse iron ore and charged into the smelting furnace 10, if necessary. In this way, the fine iron ore particles can be loaded into the smelting furnace without being scattered.

Further, since the fine grain or powdered iron ore separated by the third separator 45 is generated in the preheating device and has not passed through the preheating pre-reducing furnace, it is all returned to the preheating pre-reducing furnace.

The raw materials and auxiliary materials charged into the smelting furnace as described above are blown out together with the stirring gas from the tuyeres 25 and 26 provided on the side wall and the bottom of the smelting furnace, and the raw materials and auxiliary materials charged into the smelting furnace are blown out together with the stirring gas. Thoroughly stirred together with iron bath and slag layer. This stirring gas is exhaust gas from the preheating pre-reduction furnace or Ar5N
An inert gas such as On the other hand, oxygen supplied from the decarburization and secondary combustion nozzles 22 and 23 of the oxygen lance 21 provides a heat source sufficient to oxidize the carbonaceous material or CO gas and reduce the iron ore that is the raw material. .

The feature of the present invention is that the oxidation degree OD of the exhaust gas from the smelting furnace is reduced to 0.
4 to 0.8, the temperature is 800℃ to 1100℃, and the preliminary reduction rate of iron ore in the smelting reduction apparatus shown in Figure 1 is 30℃.
The reason for this is explained below.

FIG. 2 is a graph showing the relationship between the degree of oxidation OD and the surplus energy generated from the melt reduction apparatus of FIG. 1. In Figure 2, the shaded range is the appropriate surplus energy range when considering the energy balance of the entire steelworks, the solid line is the carbonaceous material with low volatile content, and the broken line is the carbonaceous material with high volatile content. It is related to. The number attached to each cotton is the corresponding preliminary reduction rate. This figure was obtained as a result of studying the above-mentioned melting reduction equipment.According to this, if OD is smaller than 0.4, excess energy is too large and wasteful energy is generated.
If is larger than 0.8, the surplus energy is too small and the steelworks will run out of energy. However, if the volatile content of the carbon material is 40% or more, the calorific value is 7000kcal/'kg.
If the gangue content in the iron ore is less than 5%, or if the gangue content in the iron ore is 5% or more, the unit carbon content will increase, so the OD
It is conceivable that a ratio of 0.8 to 1.0 may be desirable. This is achieved when the pre-reduction rate is set to 30% or less as shown in Figure 2, and increasing this to more than 80% is achieved by preheating and pre-reducing iron ore. The residence time in the furnace becomes longer, and the degree of freedom in the operation of the melting reduction apparatus is greatly restricted.

Further, if the exhaust gas temperature is less than 300°C, the iron ore reduction reaction will not proceed, and the thermal efficiency will also be at a low level. 110 again
At 0° C. or higher, iron ore particles may condense with each other and stick to the preheating pre-reduction furnace, causing operational troubles, and furthermore, the refractories will be more likely to wear out.

In addition to the above, the present invention is characterized by separating and recovering fine or powdery ore from the exhaust gas of the preheating pre-reduction furnace 30 or the preheating device 40, and returning it to the smelting furnace to improve the yield of iron ore. ing. The effect of this will be explained with reference to FIGS. 3 and 4. 3(a), (b), and (c) show the OD on the horizontal axis and the carbon material consumption unit, surplus energy, and amount of by-product gas generated in the smelting furnace 10 on the vertical axis, respectively. FIG. As a result, the effect of separating and recovering fine or powdery ores according to the present invention is lower than that of the conventional example.
When D is 0.5, the carbon material consumption rate, surplus energy, and by-product gas generation amount are 2O0kg/THM per ton of hot metal, respectively.
This is shown as a decrease in 2Gcal/THM and 2O0ONm/THM. FIGS. 4(a) and 4(b) are graphs in which the vertical axis represents the occurrence frequency index, and the horizontal axis represents the thermal efficiency of the smelting furnace 10 and the frequency of operational troubles due to the contamination of coarse ore. As a result, the thermal efficiency of the separation and recovery was improved by about 10%, and there were almost no operational troubles such as clogging of the nozzle 24 or tuyere 25, 26 due to the incorporation of coarse particles.

Next, specific numerical values will be listed in this example.

As carbon material, coal was used at 1124 kg/THM (per ton of hot metal produced, the same applies hereinafter), oxygen was used at 798 Nm/THM,
When used, the OD was 0.4 and the heat transfer efficiency was 90%.

[Effects of the present invention] According to the present invention, combustion of CO gas by oxygen from the secondary combustion nozzle provided in the oxygen lance and stirring gas from the tuyere provided on the wall and bottom of the smelting furnace are achieved. By blowing, the degree of oxidation of the gas generated in the smelting furnace can be adjusted to 0.4 to 0.8, the humidity of the gas can be adjusted to 300 to 1100°C, and the preliminary reduction rate can be 30% or less. The thermal efficiency of the furnace can be improved, and at the same time, the surplus energy of the melting reduction device can be made appropriate for the energy balance of the entire steelworks. In addition, fine or powdery ore is separated from the exhaust gas of the preheating pre-reducing furnace, and the ore is blown into the tuyere or the special nozzle of the oxygen lance together with the carrier gas, improving thermal efficiency and eliminating operational troubles caused by coarse grains being mixed in. You can.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the process used in the smelting reduction method of the present invention, Figure 2 is a graph showing the relationship between the degree of oxidation (OD) of exhaust gas and surplus energy according to the present invention, and Figure 3 is a diagram showing the relationship between the oxidation degree (OD) of exhaust gas and surplus energy according to the present invention. A graph showing the relationship between OD, carbon material consumption rate, surplus energy and by-product gas in comparison with the conventional example, and Figure 4 is a graph showing the relationship between thermal efficiency, magnitude of operational troubles, and frequency of occurrence. It is a diagram. DESCRIPTION OF SYMBOLS 10... Smelting furnace, 11... Iron bath, 12... Slag layer, 14... Raw material chute, 15... Gas conduit, 16... First separation device, 21...・Oxygen lance,
22.23.24... Nozzle, 25.26... Tuyere, 27.28... Pressurizing device, 30... Preheating preliminary reduction furnace, 35... Second separation device, 40...・・Preheating device,
41...Switching valve, 42...Shutoff valve, 45...
Third separation device.

Claims (4)

[Claims] (1) The ore is preheated and pre-reduced in a fluidized bed type preheating pre-reducing furnace and charged into the smelting furnace together with carbonaceous material and slag material. Oxygen is blown from the top-blowing oxygen lance and the side wall of the smelting furnace is heated and pre-reduced. and a method of melting and reducing ore by blowing stirring gas through tuyeres provided at the bottom of the furnace, the temperature of the gas introduced from the smelting furnace to the preheating pre-reduction furnace being 300 to 1100.
°C, the degree of oxidation of the gas produced in the smelting furnace, [(H_2O+CO_2)/(H_2+H_2O+CO
+CO_2)] from 0.4 to 0.8, and the pre-reduction rate in the pre-heated pre-reduction furnace is set to 30% or less, and the ore fine particles carried over from the pre-heated pre-reduction furnace are separated from the exhaust gas, and the separated fine particles are A part or all of the carbon is returned to the preheated pre-reducing furnace, and if there is any residue, it is left in the preheated high-temperature state and mixed with plain or powdered coal material, and is then heated in a dedicated furnace installed in the tuyere or oxygen lance. A smelting reduction method characterized by blowing into the smelting furnace through a nozzle. (2) The smelting reduction method according to claim 1, characterized in that the pre-reduced coarse and fine ores are mixed and charged into the smelting furnace from above by falling by gravity. (3) Coarse-grained or lumpy carbonaceous material is charged into the smelting furnace from above by falling by gravity. Claim 1
The melting reduction method according to any one of Items 1 to 2. (4) The ore is preheated and pre-reduced in a fluidized bed type preheating pre-reduction furnace and charged into a smelting furnace along with carbon material and slag material, and is top-blown with an oxygen nozzle for decarburization and secondary combustion. There is a device for melting and reducing ore by blowing oxygen from an oxygen lance and stirring gas from tuyeres provided on the side wall and bottom of a smelting furnace, the oxygen lance having a nozzle for blowing powder; , a first separation device that separates powder from the exhaust gas of the smelting furnace, a second separation device that separates the powder from the exhaust gas of the preheating pre-reduction furnace, and the exhaust gas and raw material of the second separation device. A smelting reduction apparatus comprising: a preheating device that preheats ore introduced from a supply device; and a third separation device that separates fine ore from the exhaust gas of the preheating device 40.